as per the source code of configDef it should accept List object https://github.com/a0x8o/kafka/blob/master/clients/src/main/java/org/apache/kafka/common/config/ConfigDef.java#L97
the SMT config is defined as :enter code here

“transforms”: “EqualityCheck”,

“transforms.EqualityCheck.type”:”org.apache.kafka.connect.transforms.EqualityCheckOnFields$Value”,

“transforms.EqualityCheck.fields.notEquality”: “field1, field2”,

“transforms.EqualityCheck.fieldValues.notEquality”: [[9, 0, null, 4.8234, 9.9999],
[“pol”, “POC”, “”, null ]],

And it works when I test it in my local but when i actually deploy the connector config it throws me an error below:

{“error_code”:500,”message”:”Cannot deserialize value of type java.lang.String from Array value (token JsonToken.START_ARRAY)n at [Source: REDACTED (StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION disabled); line: 35, column: 52] (through reference chain: java.util.LinkedHashMap[“transforms.EqualityCheck.fields.notEquality”])”}

the EqualityCheckOnFields Class:

public class EqualityCheckOnFields<R extends ConnectRecord<R>> implements Transformation<R> {

    private static final Logger LOG = LoggerFactory.getLogger(EqualityCheckOnFields.class);
    private static final String PURPOSE = "field validation";
    
    public static final ConfigDef CONFIG_DEF = new ConfigDef()
        .define("fields.notEquality", ConfigDef.Type.LIST, Collections.emptyList(), ConfigDef.Importance.MEDIUM, "List of fields for not-equality check")
        .define("fieldValues.notEquality", ConfigDef.Type.LIST, Collections.emptyList(), ConfigDef.Importance.MEDIUM, "List of lists containing invalid values
....


@Override
    public void configure(Map<String, ?> props) {
        SimpleConfig config = new SimpleConfig(CONFIG_DEF, props);

        notEqualityFields = config.getList("fields.notEquality");
        notEqualityValues = parseValues(config.getList("fieldValues.notEquality"));

…

private List<List<?>> parseValues(List<?> values) {
    List<List<?>> parsed = new ArrayList<>();
    for (Object value : values) {
        if (value instanceof String) {
            // Parse String as JSON array
            try {
                parsed.add(new ObjectMapper(`enter code here`).readValue((String) value, List.class));
            } catch (Exception e) {
                throw new ConfigException("Invalid JSON format in list values: " + value, e);
            }
        } else if (value instanceof List) {
            // If already a List, cast directly
            parsed.add((List<?>) value);
        } else {
            throw new ConfigException("Unexpected value type in list: " + value.getClass().getName());
        }
    }
    return parsed;
}